Sustainable composite building materials and related methods of manufacture

ABSTRACT

Sustainable composite materials for interior spaces and related methods of manufacture are provided. In one aspect of the invention, the sustainable composite materials include a load-bearing stud. The load-bearing stud includes a plurality of woven burlap layers impregnated with a magnesium oxide resin. The load-bearing stud is formed by creasing a woven burlap sheet to form multiple foldable panels, wetting the foldable panels with a curable resin, layering the foldable panels to achieve a multi-layered prepreg, pressing the multi-layered prepreg to distribute the resin therethrough, compacting the multi-layered prepreg within a mold cavity having the exterior shape of the load-bearing stud, and curing the multi-layered prepreg, wherein the resin includes a mixture of mono-potassium phosphate and magnesium oxide. The load-bearing stud provides a lightweight, dimensionally stable, and environmentally-friendly composite structure to replace lumber studs and metal studs in building constructions.

FIELD OF THE INVENTION

The present invention relates to composite building materials and, moreparticularly, impregnated burlap building materials and related methodsof manufacture.

BACKGROUND OF THE INVENTION

Composite materials generally include a combination of two or moreconstituent materials to achieve a finished product having superiormechanical or chemical qualities. Composite materials are increasinglycommon across a range of technology areas. For example, compositematerials have been used in the manufacture of sporting equipment,automobile bodies, and aerospace structures.

More recently, composite materials have been used in the manufacture ofexterior building materials, including both structural andnon-structural materials. For example, composite decking includes acombination of wood and plastic fibers, and is generally more resistantto animals, insects and warping than traditional wood decking.

Despite their advantages, composite materials can in some instances beharmful to the environment. For example, composite building materialscan include component ingredients that are not recyclable or that do notoriginate from sustainable sources. Also by example, composite buildingmaterials can take many decades to decompose, and can release chemicalsthat are harmful to local ecosystems.

The use of naturally occurring biomaterials in the manufacture ofcomposite building materials can overcome at least some of theshortcomings noted above. Accordingly, there remains a need for improvedcomposite building materials including component biomaterials. Inparticular, there remains a need for improved interior compositebuilding materials that are biodegradable, that are generally free ofharmful chemicals, and that meet or exceed the structural qualities ofexisting materials.

SUMMARY OF THE INVENTION

Sustainable composite materials for interior spaces and related methodsof manufacture are provided. In a first aspect of the invention, thesustainable composite materials include a load-bearing stud. Theload-bearing stud includes a plurality of woven burlap layersimpregnated with a magnesium oxide resin to form a hardened structurewhen cured. The load-bearing stud includes a base and left and rightlegs to form a wide variety of cross-sections, including U-shapedcross-sections and C-shaped cross-sections. The load-bearing studadditionally provides a lightweight, dimensionally stable, andenvironmentally-friendly composite structure to replace conventionallumber studs and conventional metal studs in building constructions.

In another aspect of the invention, a method for forming a load-bearingstud is provided. The method includes creasing a woven burlap sheet toform a plurality of foldable panels, wetting the panels with a curableresin, folding the foldable panels to achieve a multi-layered prepreg,pressing the multi-layered prepreg to distribute the resin therethrough,compacting the multi-layered prepreg within a mold cavity having thedesired exterior shape of the load-bearing stud, and curing the foldedprepreg, wherein the curable resin includes a mixture of mono-potassiumphosphate and magnesium oxide.

In still another aspect of the invention, a modular wall panel assemblyis provided. The modular wall panel assembly includes a first magnesiumoxide wall panel, a second magnesium oxide wall panel, and a pluralityof load-bearing studs interposed between the first and second magnesiumoxide wall panels, wherein the plurality of load-bearing studs include aplurality of woven burlap layers impregnated with a magnesium oxideresin. The load-bearing studs include an elongate bottom stud, anelongate top stud, and a plurality of vertical studs spanning the heightof the first and second wall panels, wherein the plurality ofload-bearing studs are bonded to the magnesium oxide wall panels with anadhesive. The modular wall panel assembly can include digital printingthereon, and can further optionally include embedded wires or cables.The modular wall panels can be sized for use as a floor-to-ceiling panelor as a load-bearing deck to deck panel in commercial and residentialconstructions.

These and other advantages and features of the invention will be morefully understood and appreciated by reference to the description of thecurrent embodiments and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a C-channel manufacturing operation inaccordance with one embodiment of the present invention.

FIG. 2 is an illustration of a C-channel manufacturing operation inaccordance with another embodiment of the present invention.

FIG. 3 is a cross-sectional view of an extruded mold for forming aC-channel in accordance with one embodiment of the present invention.

FIG. 4 is a flow chart illustrating a method of manufacturing asustainable load-bearing member in accordance with one embodiment of thepresent invention.

FIG. 5 are schematic illustrations of a U-channel and a C-channel.

FIG. 6 is a schematic illustration of a pre-fabricated wall panelassembly in accordance with an embodiment of the present invention.

FIG. 7 is a flow chart illustrating a method of manufacturing asustainable wall panel assembly in accordance with an embodiment of thepresent invention.

FIG. 8 is an illustration of a wall panel assembly manufacturingoperation in accordance with an embodiment of the present invention.

FIG. 9 is an illustration of a pre-fabricated deck-to-deck wall panel.

FIG. 10 is an illustration of a pre-fabricated floor-to-ceiling wallpanel.

FIG. 11 is an illustration of a pre-fabricated freestanding spacedivider.

DESCRIPTION OF THE CURRENT EMBODIMENTS

The current embodiments relate to sustainable composite materials forinterior spaces, and in particular, load-bearing studs andpre-fabricated wall panels, as well as related methods of manufacture.In these embodiments, the sustainable composite materials include, asone component, cellulose-based plant fibers, and in particular burlap,also referred to as jute and hessian. The cellulose-based plant fiberscan be unwoven or woven, for example woven burlap sheets originating inspooled rolls. The sustainable composite materials also include, asanother component, an aqueous resin to form a hardened matrix. Theaqueous resin can include magnesium oxide and mono-potassium phosphate,optionally in a ratio between 1:1 and 1:3 by weight. The aqueous resincan be substantially free of chemicals that may be harmful to theenvironment, including for example silica and boric acid.

Referring now to FIGS. 1-4, a method for manufacturing a sustainablecomposite load-bearing member will now be described. The methodinitially includes feeding a woven burlap mat 20 through a creasingstation 22 to crease the woven burlap mat 20 into a plurality offoldable panels. The creases extend longitudinally along the length ofthe burlap mat, such that the foldable panels can fold over each otherto form a multi-layered structure. For example, two creases separate theburlap mat into thirds, allowing the outer two segments to fold over asingle central segment into a three-ply mat. Also by example, threecreases separate the burlap mat into fourths, allowing the outer twosegments to each fold over one of two central segments, which then foldover each other to form a four-ply mat.

The method further includes wetting the woven burlap mat 20 with acurable resin. The curable resin includes a homogenous dry mixture andan aqueous solution, optionally being mixed immediately before thewetting application to prevent premature setting. The homogenous drymixture includes magnesium oxide and mono-potassium phosphate in thepresent embodiment. The ratio of magnesium oxide to mono-potassiumphosphate is optionally between about 1:1 and about 1:3 by weight, whilein other embodiments the ratio can vary outside this range. Themagnesium oxide can be present in the dry mixture between about 5 and 50percent by weight, while mono-potassium phosphate can be present in thedry mixture between about 15 to 70 percent by weight. Other ingredientscan also be added to the dry mixture as desired. Exemplary dry mixturesare also set forth in U.S. Pat. No. 7,429,290 to Lally, the disclosureof which is hereby incorporated by reference in its entirety. The drymixture is then thoroughly mixed with the aqueous solution, for examplewater. Suitable mixing times can vary, but can include between severalseconds to several minutes, optionally using a commercial mixer 24. Thewater is optionally applied at less than room temperature and betweenabout 15 and 55 percent by weight of the dry mixture to slow setting ofthe resin.

Once the burlap mat is wetted with a curable resin, optionally using ascrew auger 26, additional plies of burlap can be wetted and added tothe original burlap mat 20. For example, where the burlap mat includestwo crease lines, one or more additional plies can be layered over thesingle central segment. The burlap mat then passes through a foldingstation 28 to achieve a multi-layered prepreg. As the term is usedherein, prepreg means a fiber structure that has been wetted orimpregnated with a resin prior to curing. The multi-layered prepreg thenpasses through a pressing station 30 to evenly distribute the resinthroughout the voids in the burlap mat. For example, the pressingstation can include multiple rollers. As the multi-layered prepreg exitsthe folding station, the rollers extend transversely to the direction oftravel to intercept and flatten the multi-layered prepreg across itswidth.

The method further includes compacting the multi-layered prepreg withinan extruded mold having an internal mold cavity, wherein the internalmold cavity includes the desired exterior shape of the load-bearingmember. A cross-sectional view of the extruded mold 32 is shown in FIG.3. The extruded mold 32 includes an interior (or male) mold portion 34and an exterior (or female) mold portion 36. The interior mold portion34 includes first and second fingers 38, 40 to mate with correspondingfirst and second grooves 42, 44 of the exterior mold portion 36. Theexterior mold portion 36 additionally includes first and second hingelines 46, 48 to permit a left leg 50 to close with respect to theinterior mold portion 34 and a right leg 52 to close with respect to theinterior mold portion 34. The interior and exterior mold portions 34, 36including opposing surfaces 54, 56 that are urged into registrationagainst the multi-layered prepreg 58, optionally under a source ofexternal pressure. Once closed, the extruded mold 32 provides thedesired three-dimensional shape to the multi-layered prepreg 58 whileallowing the resin to cure, optionally for a period of one hour or more.

One example of a curing station is depicted in FIG. 2. The curingstation 60 includes a continuous belt 62 having a plurality of exteriormold portions 36 affixed thereto. For example, the continuous belt 62can include a given number of exterior mold portions 36 extendingtransverse to the direction of travel. The wetted multi-layer prepreg isplaced into an exterior mold portion 36, the interior mold portion 34 isinserted, and the exterior mold portion 36 is closed, urging theopposing surfaces 54, 56 into registration against the wettedmulti-layered prepreg. When the mold 32 reaches the end of the curingstation 60, the mold 32 is opened, and a partially-cured load-bearingmember 58 is removed from the mold 32. The partially-cured load-bearingmember 58 is allowed to cure at a final curing cart 64, also depicted inFIG. 2, while internal mold portions 34 are returned to the beginning ofthe conveyor 62 along an upper return conveyor 66. Though not shown,either or both of the current station 60 and the curing cart 64 caninclude an oven or other heat source to advance the curing of themulti-layered prepreg. In the present embodiment, however, curing isperformed substantially at room temperature. Once cured, a finishingprocess is applied to the load-bearing member. The finishing process caninclude structural aspects such as deburring, sanding or grinding anyimperfections, and can include aesthetic aspects such as painting orpolishing.

To reiterate, and with reference to the flow chart of FIG. 4, thepresent manufacturing method generally includes mixing a resin at step70, wetting a burlap mat with the resin at step 72, optionally precededby folding the burlap mat into a desired number of layers, transferringthe wetted burlap mat into a mold at step 74, closing the mold at step76, curing the wetted burlap mat at step 80, and opening and removing ahardened stud from the mold for further processing at step 82. Thepresent manufacturing method can optionally include a run rate of atleast 40 feet per minute using two-pieced, extruded replaceable molds 32shown in FIG. 3. In modifications of the manufacturing method however,the wetted burlap mat can be roll formed into the desired shaped, ratherthan being inserted into a two-pieced extruded mold.

The resulting load-bearing member can assume a wide variety of lengthsand cross-sectional shapes. The load-bearing member can include standardlumber dimensions, including 2″×4″ and 2″×6″ for example. Two exemplarycross-sectional shapes are depicted in FIG. 5, in particular a U-channel84 and a C-channel 86. Both of the U-channel 84 and the C-channel 86include a base segment 88 and left and right leg segments 90, 92. TheC-channel 86 additionally includes a left lip 94 and a right lip 96 toprovide added torsional strength. Other cross-sectional shapes may beused in other embodiments. For example, the load-bearing member caninclude an I-beam cross-section. The resulting load-bearing member canbe both lightweight and strong, drawing its compressive and tensilestrength from the fibrous resin matrix.

The load-bearing member can additionally be used to form apre-fabricated wall panel assembly, particularly for interior use as afloor-to-ceiling wall panel, a deck-to-deck wall panel, or as afree-standing wall panel. Referring now to FIG. 6, a pre-fabricated wallpanel assembly is illustrated and generally designated 100. Thepre-fabricated wall panel assembly 100 includes first and secondwallboards 102, 104 and a plurality of load-bearing studs 106, 108, 110,112, 114, 116 interposed therebetween. The wallboards 102, 104 include amolded composition of magnesium oxide and magnesium chloride, beinggenerally fire resistant, water resistant, and substantially free ofsilicate-based products. The wallboards 102, 104 are generally parallelto each other, being spaced apart by the width of the load-bearingstuds, in this instance 4 inches. The load-bearing studs include alaterally elongate bottom stud 106, a laterally elongate top stud 108,and a plurality of vertical studs 110, 112, 114, 116 spanning the heightof the first and second wallboards 102, 104. The load-bearing studs areU-channels in the illustrated embodiment, but can include C-channels orother cross-sections in other embodiments.

The load-bearing studs are bonded to the first and second wall panelsusing an adhesive in the present embodiment, optionally a hotmelt fromHenkel AG & Co. In other embodiments conventional metal fasteners areused to secure the load-bearing studs to the first and second wallpanels. The wall panel assembly can include embedded wires or cables,and can include a painted exterior. For example, the wall panel assemblycan include a digital printing thereon, optionally a latex printing.

Referring now to FIG. 7, a method for manufacturing the wall panelassembly will now be described. The method generally includes providingmagnesium oxide wallboard at step 120 and cutting the studs to length atstep 122. At step 124, the studs are bonded to the wallboard using anon-toxic adhesive, for example a hotmelt. A holding press then pressesthe wall panel assembly to the desired thickness at step 126. Steps 128and 130 include a hardware assembly and an electrical finish,respectively. At step 132 the wall panel assembly is inspected, and atstep 134 the wall panel assembly electrical components are tested. Oncepassing inspection, the wall panel assembly is wrapped and stacked forshipment at step 138.

The above process is graphically illustrated in FIG. 8. As shown,additional hardware, trim and electrical components can be added in aline manufacturing process that is both scalable and partiallyautomated. The completed wall panel assemblies can additionally bemanufactured to be both fire rated and acoustically rated. The completedwall panel assemblies can be used across a wide range of applications.For example, pre-fabricated wall panel assemblies can be used in themanufacture and renovation of low-rise offices, high-rise offices,healthcare facilities, educational facilities, hotels, manufacturingfacilities, and warehousing facilities. In these and other facilities,the pre-fabricated wall panel assemblies can be used as deck-to-deck,floor-to-ceiling, and free-standing space dividers as generally depictedin FIGS. 9-11.

The above embodiments of the present invention therefore providepre-fabricated wall panel assemblies that are largely renewable andbiodegradable. The wall panel assemblies leverage the benefits ofcellulose-based biomaterials, and in particular burlap, and are in manyinstances visually superior to existing products. As one of ordinaryskill in the art will appreciate, the above methods for manufacturingburlap fiber-reinforced studs and wall panel assemblies may be tailoredto have specific properties and may be subject to further processing notexpressly set forth above.

The above description is that of current embodiments of the invention.Various alterations and changes can be made without departing from thespirit and broader aspects of the invention as defined in the appendedclaims, which are to be interpreted in accordance with the principles ofpatent law including the doctrine of equivalents. This disclosure ispresented for illustrative purposes and should not be interpreted as anexhaustive description of all embodiments of the invention or to limitthe scope of the claims to the specific elements illustrated ordescribed in connection with these embodiments. Any reference toelements in the singular, for example, using the articles “a,” “an,”“the,” or “said,” is not to be construed as limiting the element to thesingular.

1. A method for forming a load-bearing member, comprising: creasing awoven burlap sheet to form a plurality of foldable panels; wetting thefoldable panels with a magnesium oxide resin; folding the foldablepanels to achieve a multi-layered prepreg; pressing the multi-layeredprepreg to distribute the magnesium oxide resin; compacting themulti-layered prepreg within a mold cavity having the exterior shape ofthe load-bearing member; and curing the multi-layered prepreg.
 2. Themethod according to claim 1 wherein the curing step is performed at roomtemperature.
 3. The method according to claim 1 wherein the resinincludes an agitated mixture of magnesium oxide, mono-potassiumphosphate and water.
 4. The method according to claim 3 wherein theresin includes a ratio of mono-potassium phosphate and magnesium oxidebetween about 3:1 and 1:1 by weight.
 5. A composite building membercomprising: a plurality of woven burlap layers pre-impregnated with amagnesium oxide resin to form a hardened load-bearing stud when cured atsubstantially room temperature.
 6. The composite building member ofclaim 5 wherein the load-bearing stud includes a generally U-shapedcross-section.
 7. The composite building member of claim 5 wherein theload-bearing stud includes a generally C-shaped cross-section.
 8. Thecomposite building member of claim 5 wherein the load-bearing studincludes a base segment and left and right leg segments.
 9. Thecomposite building member of claim 5 wherein the resin is substantiallyfree of silica.
 10. The composite building member of claim 5 wherein theresin is substantially free of boric acid.
 11. A modular wall panelassembly comprising: a first magnesium oxide wall panel; a secondmagnesium oxide wall panel; and a plurality of studs interposed betweenthe first and second magnesium oxide wall panels, wherein the pluralityof studs include a plurality of woven burlap layers pre-impregnated witha magnesium oxide resin.
 12. The modular wall panel assembly of claim 11wherein the plurality of studs include: an elongate bottom stud; anelongate top stud; and a plurality of vertical studs spanning the heightof the first and second wall panels.
 13. The modular wall panel assemblyof claim 11 wherein the plurality of studs are bonded to the first andsecond wall panels with an adhesive.
 14. The modular wall panel assemblyof claim 13 wherein the adhesive includes a hotmelt.
 15. The modularwall panel assembly of claim 11 wherein the modular wall panel assemblyincludes embedded wires or cables.
 16. The modular wall panel assemblyof claim 11 wherein at least one of the first and second wall panelsincludes a digital printing thereon.
 17. The modular wall panel assemblyof claim 11 wherein the wall panels and the load-bearing studs aresubstantially free of boric acid and silica.
 18. The modular wall panelassembly of claim 11 wherein the wall panels and the studs are moldresistant and fire resistant.